Breast removal is an effective way to reduce - but not remove - the chance that women at high risk will develop breast cancer, scientists have found.

US researchers studied 639 women with a family history of breast cancer who had undergone surgery to remove both breasts as a precaution.

Of those studied, 214 were thought to be at risk of getting cancer and 425 had a moderate risk of developing the disease, the New England Journal of Medicine reports.

The average age of the women when they underwent surgery was 42 years.

Some women are genetically predisposed to developing cancer

According to scientific predictions, without precautionary surgery 37.4 breast cancers would have developed among the moderate-risk group.

However, only four breast cancers actually occurred - a risk reduction of 90%.

The 214 women in the high-risk group were compared with 403 women at high risk who did not undergo surgery.

Almost one in four of the women - 156 out of 403 - who did not undergo surgery developed breast cancer.

But just three out of the 214 women who did have a mastectomy developed the disease - again a reduction in risk of 90%.

Julietta Patnick, national coordinator of the NHS breast screening programme, said: "It must be made clear to women considering a prophylactic mastectomy because they have a very strong family history of breast cancer that surgery will not completely remove the chance of getting breast cancer."